How do Marxists derive their normative beliefs?

If I take Marxism to be couched in a purely Materialist ontology where it describes objectively how society is transforming, why should I care about the rights of working class and the political agenda of any Marxist movement? Marx is simply describing an independent process of economic class conflict and reconciliation in a universe which is nothing more than a random flux of particles. Why should I welcome the outcomes of dialectical materialism anymore than the drifting of the Milkyway galaxy out into deep space? Why is it my duty to advocate for the interests of the poor? To reduce economic inequality?

Human beings have material needs and a capacity to coordinate efforts to serve those needs. When those needs are not being met and coordinated efforts are to blame, then one has a basis for normative condemnation of those coordinated efforts (in this case, capitalism).

Human beings have material needs and a capacity to coordinate efforts to serve those needs. When those needs are not being met and coordinated efforts are to blame, then one has a basis for normative condemnation of those coordinated efforts (in this case, capitalism).

Why is it "wrong" if those needs are not met? What, in Marxist theory, makes it "wrong"? Granted that some people "care" about such things, why, per Marxism, *should* they care? That's the sort of question OP is asking. I think it is a good question (kind of wish I'd thought of it, actually): what is the ground for normative beliefs in Marxism? I would have asked what is the ground for "morality" in Marxism, given dialectical materialism.

So-called economist here: I've found that once you start reading Marx, you start to see the world in terms of exploiter and exploitee, since his analysis revolves around the concept that profits are derived from exploiting workers. Veblen and later Galbraith pointed out that even in a socialist society, workers need to be "exploited" in order to garnish adquate "surplus" to produce what the state deems to be important e.g. military resources in USSR.

Wow, this really made me think. You should write a paper on this idea submit to APSR.

If I take Marxism to be couched in a purely Materialist ontology where it describes objectively how society is transforming, why should I care about the rights of working class and the political agenda of any Marxist movement? Marx is simply describing an independent process of economic class conflict and reconciliation in a universe which is nothing more than a random flux of particles. Why should I welcome the outcomes of dialectical materialism anymore than the drifting of the Milkyway galaxy out into deep space? Why is it my duty to advocate for the interests of the poor? To reduce economic inequality?

Wow, this really made me think. You should write a paper on this idea submit to APSR.
If I take Marxism to be couched in a purely Materialist ontology where it describes objectively how society is transforming, why should I care about the rights of working class and the political agenda of any Marxist movement? Marx is simply describing an independent process of economic class conflict and reconciliation in a universe which is nothing more than a random flux of particles. Why should I welcome the outcomes of dialectical materialism anymore than the drifting of the Milkyway galaxy out into deep space? Why is it my duty to advocate for the interests of the poor? To reduce economic inequality?

With the Euros controlling the journal, it will almost certainly land.

If I take Marxism to be couched in a purely Materialist ontology where it describes objectively how society is transforming, why should I care about the rights of working class and the political agenda of any Marxist movement? Marx is simply describing an independent process of economic class conflict and reconciliation in a universe which is nothing more than a random flux of particles. Why should I welcome the outcomes of dialectical materialism anymore than the drifting of the Milkyway galaxy out into deep space? Why is it my duty to advocate for the interests of the poor? To reduce economic inequality?

Despite the down votes, this is actually an interesting question. You are right, if dialectic materialism makes communism a historical inevitability, as Marx believed, then you have no reason to care for normative issue. Why advocate for the working class? It is written in stone that they will succeed in overthrowing the capitalist system.

Of course, the failure of this actually happening within the predicted time span led to a new wave of communists that recognized capitalism's ability to evade its own destruction. The Critical Theorists put back ideology as a superstructure that matters above the base. Pure materialist Marxism that concentrated solely on material factors (supposedly, IR constructivists point out convincingly that the exploiter-exploited relation is actually a social relation rather than a material fact) was discredited.

Even though OP's point has been made ten thousand times before, it has never been answered. Facts aren't values. A political activist can't base his activism on Marxist social science (such as it is). But in the real world, this distinction is ignored by activists and Marxist social scientists all the time. Marxism, then, becomes just an elaborate rhetoric that gives the political activist the illusion of having a scientific grounding for his normative demands.

Okay, this is too easy. Kantian ethics via his account of human nature. Materialism =/= Nihilism. Moral realism through mathematics offering a series of "rules" that hold universally but do not govern materially. So, it is up to us to realise the normative realm and create a BRIDGE. Uh oh, bridge talk.

All human values emanate from the Hegelian Absolute. The spirit of justice, fairness, equality is what makes us authentic and moves human history forward.

How else can we explain the Enlightenment, the American Revolution, the French Revolution, the Russian Revolution, the New Deal . . . without the Absolute? Moreover, the billions of acts of kindness, courtesies that humans share on a daily basis are a direct product of the Absolute.

Put differently, it is quite literally impossible to understand the existence of humans (the survival instinct) as well as human existence without reference to the Absolute.

A lot of snark itt because leftist pinheads have no answer to this and they know it.
Marx presupposed the Hegelian Absolute. This is where the values of justice and equality inhere.
Oh, okay then. It's the "Hegelian Absolute". Marxism is real science, folks.

All human values emanate from the Hegelian Absolute. The spirit of justice, fairness, equality is what makes us authentic and moves human history forward.
How else can we explain the Enlightenment, the American Revolution, the French Revolution, the Russian Revolution, the New Deal . . . without the Absolute? Moreover, the billions of acts of kindness, courtesies that humans share on a daily basis are a direct product of the Absolute.
Put differently, it is quite literally impossible to understand the existence of humans (the survival instinct) as well as human existence without reference to the Absolute.

This is a cop out. The normative beliefs and values are just behavioral norms selected for in our biological evolution. Are you saying Marxism denies the theory of evolution?